You may know it as a nitrate; others call it saltpeter. Whatever it’s called, this substance is used in explosives, fertilizer and food preservation.

The Humberstone and Santa Laura saltpeter works in Chile’s province of Iquique were established in the late 1800s. They have been closed for more than 50 years, but they were once a part of northern Chile’s robust saltpeter industry. Despite the harshness of the Pampas desert, one of the driest regions on Earth, the towns thrived from the 1880s to the 1930s, when the introduction of synthetic saltpeter cut into the industry. Mining ceased in 1959, and the communities were declared monuments in 1970.

These were company towns that developed their own culture and even language. Each town contained an industrial and urban quarter, the latter encompassing schools, tennis courts and residential buildings.

The towns were designed around the harsh environment. Shaded walkways were built near buildings, and homes had zinc roofs to reflect heat. A war over the nitrate brought Peru, Chile and Bolivia to battle (Chile won) and shaped the economy of the area for years.

Craco, Italy

The very thing that kept Craco safe may have proved its undoing.

The southern Italian village was built between the 9th and 10th centuries BC on a 1,300-foot summit, so much the better to see approaching enemies. Unfortunately, there’s quite a lot of seismic activity in the area, which continually damaged the rocky village’s buildings and undermined the stability of their foundations. In 1991, a landslide forced out the last residents.

Craco, however, is not completely forgotten. Parts of movies have been shot there, notably Mel Gibson’s “The Passion of the Christ” (2004) and the James Bond thriller “Quantum of Solace” (2008).

Tazart, Morocco

About 250 miles south of Marrakech, Morocco, lies Tazart, once home to a mellah, or Jewish quarter.

Morocco’s Jews began living in mellahs, which were fortified, as early as the 1400s. Later, all Jewish residents were required to live in a mellah.

It is said that Charles Eugene de Foucauld, a native of Strasbourg, France, lived in Tazart in the 1880s as part of his exploration of Morocco. (He later become a priest and ascetic and was killed in 1916 by rebels.)

Tazart was abandoned when the region dried up. After the establishment of Israel in the late 1940s, most Moroccan Jews moved there.